Voltage regulation



Sept. 7, 1954 w. H. BlxBY VOLTAGE REGULATION Filed June 29, 1948/NVE/VTOF? W. H. B/XBV BV ATTORIVEVv Patented Sept. 7, 1954 y VOLTAGEREGULATION William H. Bixby, Detroit, Mich., assigner to Donald R.Middleton and Stanley M. Hanley, a copartnership, doing business asPower Equipment Company, Detroit, Mich.

Application June 29, 1948, Serial No. 35,948

8 Claims.

This invention relates to voltage regulation and particularly to arectier for supplying current to a load at substantially constantvoltage.

An object of the invention is to provide improved regulated rectifyingapparatus for supplying direct current to a load.

In accordance with an embodiment of the invention herein shown anddescribed for the purpose of illustration, there is provided a polyphaserectifier comprising a plurality of grid controlled, gas-filled, spacecurrent devices, one for each phase, for rectifying current from analternating current supply source, the rectied current being supplied toa load. While a two-phase rectif-ler is specifically shown, theinvention is also applicable to rectiiiers having a larger number ofphases. Means are provided for generating large amplitude voltage pulseshaving a steep Wave front which are impressed upon the controlgrid-cathode circuits of the rectifier tubes repeatedly in successionfor causing the tubes, respectively, to conduct space current duringsuccessive periods in which the anodes of the respective tubes arepositive with respectl to the cathodes. When conduction is started ineach tube, it will continue to pass space current during a time intervalequal to that of a half cycle of the alternating current supply source.There is provided for generating the triggering pulses for startingconduction in the rectier tubes a circuit arrangement comprising aplurality of space current devices or pulse generating triodes, one foreach rectier tube. There is impressed upon the control grid-cathodecircuit of each of the pulse generating devices a voltage having analternating voltage component derived from the alternating currentsupply source and a direct voltage component having variationsycorresponding to load voltage changes, the series of triggering pulsesbeing advanced or delayed in response to load voltage changes to controlthe current supplied to the load and thereby to control the loadvoltage.

The invention will now be described in greater detail with reference tothe accompanying drawing, the single figure of which is a schematic Viewof a regulated rectifier embodying the invention.

Referring to the drawing, there is provided a. rectifier comprisingthree-electrode, gas-filled, space current devices I and II forrectifying current from an alternating current supply source I2 and forsupplying the rectified current to a load I3. A two-phase rectifier isshown for the sake of simplicity, the invention also being applicable toa rectifier having a smaller or larger number of phases, a six-phaserectifier for example. There is provided a transformer having a primaryWinding I4 connected to the alternating current source l2 and asecondary Winding I5. There is provided a second transformer having aprimary Winding 25 connected to the supply source I2 and havingsecondary windings i6, il and I8. The end terminals of transformerWinding I5 are connected to the anodes, respectively, of rectier tubesI0 and I I. and a mid-tap of winding I5 is connected through inductivereactance element I9 of a ripple lterto the negative load terminal, thefilter also comprising a shunt condenser 20 connected across the load.The cathodes of tubes I0 and II are connected to the positive loadterminal. The control grids of tubes I0 and II are connected byresistorsZI and 22, each having a resistance of the order of 47,000ohms. A bridge type rectifier 23 havingan asymmetrcally conductingelement in each arm of the bridge has its input terminals connected tothe terminals of secondary transformer Winding I6. The positive outputterminal of rectier 23 is connected to the cathodes of tubes Ill and Iland the negative output terminal of rectifier 23 is connected to thecommon terminal of resistors 2| and 22. A iiltering condenser 24 and ableeder resistor 26 are connected across the output terminals ofrectifier 23. The control grid of each of tubes I0 and II is thusnegatively biased with respect to its cathode to prevent space currentconduction in each tube in the absence of a positive potentialtriggering or starting pulse impressed upon the control grid withrespect to the cathode. v

There is provided an amplier comprising a space current device 30 forsetting up a direct voltage having variations corresponding to loadvoltage changes but of larger amplitude. Space current is supplied totube 30 from an auxiliary rectier comprising a full Wave rectifier tube3l. The anodes of tube 3l are connected to the end terminals oftransformer Winding II and the mid-terminal of the winding is connectedto the negative output terminal of the rectier. A ripple lter comprisinga series inductive reactive element 32 and a shunt condenser 33 isprovided, the cathode of tube 3l being connected through inductanceelement 32 to the positive output terminal of the rectiiier. Thepositive terminal of rectier 3l is connected through a resistor 34 tothe anode of tube 30 while the negative output terminal of the rectiiieris connected directly to the cathode of tube 30. A

positive load terminal.

shunt current path connected to the output terminals of rectifier 3|comprises in series a resistor 35 and a cold cathode, gas-lled tube 3B.The tube 36 has the characteristic that its resistance changes inresponse to changes of current iiowing through the tube so that thevoltage across the tube remains substantially constant, output voltagechanges of rectiiier 3| appearing across resistor 35.

Two current paths are connected across the load I3, one comprisingresistor 31, potentiometer 38 and resistor 39, all in series, and theother comprising a condenser 40 and a resistor 4| in series. A pathconnecting the variable tap of potentiometer 38 and the common terminalof condenser 40 and resistor 4| comprises in series a resistor 42 and acondenser 43. The common terminal of resistor 42 and condenser 43 isconnected through a resistor 44 to the control electrode of tube 30. Thecathode of tube 38 is connected through constant voltage tube 36 to theThere is thus impressed upon the control grid-cathode circuit oi' tube38 a voltage equal to the diierence of the voltage across resistor 39and an adjustable portion of potentiometer 38 and the voltage acrossconstant voltage tube 36, these two component voltages preferably beingsuch that the control grid potential is negative with respect to thecathode potential by a suitable operating value. The network comprisingcondensers 40 and 43 and resistor 4| is provided to prevent huntingaction of the regulator circuit. Screen grid potential is supplied totube 30 from the common terminal of resistor 35 and constant voltagetube 36 through a resistor 45.

There is provided a pulse generating circuit arrangement comprising atwin triode tube 46 having two triode space current devices 41 and 48.The cathodes of triodes 41 and 48 are connected to the common terminalof resistor 35 and constant voltage tube 36. 'I'he positive terminal ofrectifier 3| is connected through a resistor 49 to the anode of triode41 and through a resistor 50 to the anode of triode 48. Resistors 49 and5U each have a resistance of the order of 22,000 ohms. One end terminalof secondary transformer winding |8 is connected through a resistor tothe control electrode of triode 41 and the other end terminal of windingI8 is connected through a resistor 52 to the control electrode of triode48, resistors 5| and 52 having a resistance of the order of 470,000ohms. A mid-terminal of transformer winding I8 is connected to the anodeof tube 30. The anode of triode 41 is connected through a condenser 53to the control grid of tube II and the anode of triode 48 is connectedthrough a condenser 54 to the control grid of tube I0, the capacitanceof each of condensers 53 and 54 being of the order of 0.05 microfarad.

The grid-cathode circuit of tube 30 comprises, in series, resistors 44,42 and 39, an adjustable portion of potentiometer 38 and constantvoltage tube 36. If the load voltage should increase, for example, thecontrol grid of tube 30 would become relatively more negative withrespect to its cathode, thus causing the voltage across resistor 34 todecrease and the potential at the anode of tube 30 to become relativelymore positive with respect to its cathode and, therefore, with respectto the positive load terminal. The voltage across resistor 35 willincrease in response to an increase of voltage of the supply source I2and vice versa. The grid-cathode circuit of triode 41 may be traced fromthe grid through resistor 5|,

the upper portion of winding I8, resistor 34 and resistor 35, to thecathode. A similar circuit may be traced for the triode 48, this circuitincluding resistor 52 and the lower portion of winding I8. The voltagesacross resistors 34 and 35 are in opposition in each of these circuitsand the voltage across resistor 34 is smaller than the voltage acrossresistor 35 so that the resultant direct voltage component in thegrid-cathode circuit is of such polarity as to make the control gridpositive with respect to the cathode. The phase of the alternatingcomponent voltage from transformer |8 impressed upon the control circuitof triode 41, for example, is preferably in phase opposition to thevoltage which is impressed from the lower portion of transformer WindingI5 upon the anode-cathode circuit of tube I.

The large resistance of resistor 5| in the gridcathode circuit of triode41, for example, limits the positive potential which can appear at thegrid with respect to the cathode to a relatively small value because ofthe grid current which flows through the resistor. As a result, when thegrid is positive, the triode will pass a fixed space current and thepotential at the anode will remain substantially fixed with respect tothe cathode up to the time when the alternating voltage component in thegrid-cathode circuit suddenly drives the grid to a negative potentialthrough the cut-off value,causing the space current to decrease rapidlyto zero. The alternating voltage component in the grid-cathode circuithas a large amplitude such that the change of grid-cathode voltage froma positive value to a negative cut-01T value will occur within a verybrief time interval, The resulting abrupt decrease of space current intriode 41 will produce an abrupt rise of the potential at the anode oftriode 41 with respect to its cathode and, therefore, with respect tothe cathode of tube This sharp, positive pulse is impressed throughcondenser 53 upon the control grid of tube II to cause it to conductspace current, this conduction continuing during a. period in which theanode of tube is positive with respect to its cathode. The sum of thevoltage across inductance element |9 and the voltage across the lowerhalf of transformer winding I5 maintains the anode of tube I I positivewith respect to its cathode until conduction is initiated in tube I0.

The circuit should be so adjusted that the potential of the anode ofamplifier tube 30 will not be appreciably less than the potential of thescreen grid of the tube for any normal operating condition. Since, withthe choke coil I9 in the input of the main lter section, full control ofthe output current will be obtained by varying the firing angle of eachof tubes I0 and over a range from zero to ninety degrees in therespective conducting half cycles of tubes II) and |I. the iiring angleshould be approximately at zero degrees when the potential of the anodeof tube 30 is approximately at the screen grid potential of tube 30. Thealternating component of the control electrode-cathode voltage of triode41, for example, is therefore preferably in phase opposition to thealternating voltage across theA lower half of transformer winding I5. Insome recti- `fiers, such as two phase rectilers employing a filter chokeI9 the inductance of which is less than a certain critical value orrectil'iers having a larger number of phases, it would be necessary toprovide a phase shifter for shifting the phase of the voltages derivedfrom source I2 and applied to the control electrode-cathode circuits ofthe pulse generating triodes like triodes 41' and 48.

An increase of the direct component of the grid-cathode voltage oftriode 41, for example, will cause the cut-off potential of the triodeto be reached later in each cycle of the alternating voltage componentof the grid-cathode voltage of the triode. As a result, the triggeringor starting pulse impressed upon the grid-cathode circuit of tube H willoccur later in the positive half cycle of the anode-cathode Voltage,that is, when the anode is positive with respect to the cathode. Theaverage voltage supplied by the rectifier to the'input of lter I9, 20 isthus decreased. A negative pulse will be produced at the anode of triode41 When space current is started in the triode due to the grid potentialpassing through the cut-off value to a positive value of potential. Thisnegative pulse will have no effect on the space current path of tube Iland it may therefore be disregarded in considering the operation of thecurrent supply circuit. The triode 48 is controlled similarly to thetriode 41 to produce recurring positive pulses for starting conductionof space current in tube l0 during half cycle periods of the alternatingVoltage from source I2 When the anode of tube I0 is positive Withrespect to its cathode.

The load voltage may be set at a desired value within an operating rangeby adjusting the variable tap of potentiometer 38. When thepotentiometer is adjusted for maximum operating voltage, the voltageacross` resistor 34 is at a relatively large value and, when the voltageof source l2 is at a minimum operating value, the voltage acrossresistor 35 is at a minimum value. Under these conditions the directvoltage component in the grid-cathode circuit of each of triodes 41 and48 is relatively small and conduction of space current in tubes l0 andIl Will occur relatively early in the positive half cycle of theanode-cathode Voltage of each of tubes l0 and Il. For any setting ofpotentiometer 38, when an increase of load voltage occurs, for eX-ample, the control grid of tube 30 will become relatively more negativewith respect to its cathode with the result that the voltage drop acrossresistor 34 will decrease. The direct voltage component in thegrid-cathode circuit of triodes 41 and 48 will thus increase to causethe starting pulses impressed upon the grid-cathode circuits of tubes l0and H to be delayed. The average voltage supplied by the rectifier toiilter i9, 20 is thus decreased to cause the initially assumed increaseof load voltage to be minimized. Similarly, When the voltage of thesupply source increases, for example, the direct component of thevoltage in the grid-cathode circuits of triodes 41 and 48 increases tocause the starting pulses for tubes I0 and Il to be delayed and therebycausing a decrease of the voltage supplied by the rectifier to iilterI9, 20. This action thus tends to prevent a rise of load voltage due tothe voltage increase of the alternating current source l2.

What is claimed is:

l. In combination, means comprising a gasfilled space current devicehaving'an anode, a cathode and a control electrode for rectifying andcontrolling the supply of rectified current from an alternating currentsupply source to a load, a second space current device having an anode,a cathode and a control electrode, means for causing current to ilow ina circuit including the space current path of said second device, meansfor setting up across a portion of said circuit red curring voltagepulses in response to interruptions of the space current in saidcircuit, said means comprising means for impressing upon a circuitconnecting said control electrode and cathode of said second device avoltage having an alternating component derived from said supply sourceand a direct component the amplitude of which varies in accordance with`load voltage variations, each of said pulses being of brief durationWith respect to the period of a half cycle of the alternating currentfrom said supply source, and means for impressing said voltage pulsesupon va circuit connecting the control electrode and cathode of saidfirst space current device for repeatedly initiating conduction of spacecurrent in said first device coincidentally with said voltage pulses.

2. A combination in accordance with claim l in which there is providedmeans for biasing the control electrode of said rst space current devicenegatively with respect to its cathode for preventing the initiation ofspace current conduction in said device except during that portion ofeach half cycle of said alternating current source when the anode ispositive With respect t0 the cathode which follows each of said voltagepulses.

3. In combination, tWo gas-lled space current devices each having ananode, a cathode and a control electrode, circuits connecting the anodeand cathode of said devices, respectively, means for impressing uponsaid circuits, respectively, out of phase alternating voltages derivedfrom an alternating current supply source, a third circuit comprising inseries order a first resistor, a second resistor, a first condenser, athird resistor, a fourth resistor and a second condenser, a source ofdirect voltage, means for connecting the positive and negative terminalsof said direct voltage source to said cathodes and to the commonterminal of said first and second resistors, respectively, means forconnecting the common terminal of said iirst resistor and said secondcondenser to the control electrode of a first of said space currentdevices, means for connecting a common terminal of said second resistorand said rst condenser to the control electrode of the second spacecurrent device, a direct current source, a fourth circuit comprisingsaid third resistor and said direct current source, a fifth circuit comprising said fourth resistor and said direct current source, thepositive terminal of said direct current source being connected to acommon terminal of said third and fourth resistors, means for connectingthe negative terminal of said direct current source to said cathodes,and means under control of said alternating current supply source forinterrupting the currents in said fourth and fth circuits respectivelyrepeatedly in succession for causing voltage pulses to be impressed uponthe control electrodes with respect to the cathodes of said spacecurrent devices, respectively, to repeatedly and successively initiatespace current conduction in said devices, respectively.

4. A combination in accordance with claim 3 in which said last-mentionedmeans comprises a third and a fourth space current device each having ananode, a cathode and a control electrode, means for connecting the spacecurrent paths of said third and fourth devices in said fourth and fthcircuits, respectively, a sixth circuit and a seventh circuit connectingthe control electrode and cathode of said third and andrai 7 fourthdevices,` respectively, each of. said; circuits having resistance oflarge magnitude therein, and means for impressing on said. sixth andseventh circuits out of phase alternating voltages derived from saidalternating currentI supply source.

5. In combination, meanscomprising` a, gaseous space current; devicehaving an anode, acathode and, a control electrode for rectifyingcurrent from an alternating current source and for controlling thesupply of the rectified current to a load, means forimpressing anegative biasing potential upon said4 control electrode with respect tosaid cathode comprising a circuit connecting said control electrode andsaid cathode, said circuit including a source of direct voltage andaresistor, means for setting up a control voltage having variationscorresponding to load voltage changes, a second space current devicehaving an anode, a cathode and a` control electrode, a resistor, a spacecurrent circuit for said second device comprising said resistor and asource of space current, a condenser, a circuit comprising saidcondenser for connecting the anode-'cathode from said alternatingcurrent source and said control voltage.

6. A regulated power supply comprising a rectier circuit including anelectron discharge device, means for impressing an alternating voltageon said rectifier circuit, an output circuit coupled to said rectifiercircuit for deriving a regulated unidirectional output voltage, a sourceof electrical waves coupled to saidoutput circuit, and means forderiving pulses from said wave source and impressing them on saidelectron discharge device, the frequency of said pulses being responsiveto variations of said output voltage, thereby to control said electrondischarge device in response to variations of said output voltage.

7. A regulated power supply comprising a., rectii'ler circuit. includinga space current device, means for impressing an alternating voltage onsaid rectifier circuit, an output circuit coupled to said rectifiercircuit for deriving a` regulated unidirectional output voltage,andmeans for generating and impressing upon said spacek current 8ldevice-intermittent pulses each of brief duration with respect to a halfcycle period of said alternating voltage for causing space currentconduction to be repeatedly initiated in said space current device, saidlast-mentioned means comprisingmeans electrically coupling said spacecurrent device to` said output circuit and responsive to variations ofsaid output voltage for controlling the relative phase of said pulseswith respect to said, alternating voltage.

8. In combination, means comprising a iirst space current device forsupplying rectiiied current from an alternating-current supply sourceyto a load circuit including a load, said device hav,- ing anl anode,` acathode and a control electrode, means for impressing a biasingpotential upon said control electrode with respect to said cathode,- asecond space current device having an` anode, aV cathode and a controlelectrode, a first circuit including a source of space currentconnectingV the anode and cathode of said second` device, means forderiving an alternating voltage from said alternating-current supplysource, means coupled to said load circuit for setting up a voltagehaving variations corresponding'to load voltage changes, a secondcircuit connecting the control electrode and cathode of said secondldevice, means for impressing upon said second circuit said alternatingvoltage and said voltage having variations corresponding to load`voltage changes, and means for deriving from said first circuit andimpressing upon the control electrode with respect to the cathode ofsaid iirst device for overcoming said biasing potential and repeatedlyinitiating space current conduction in said first device pulses thefrequency of which is responsive to said load voltage changes, therebycontrolling said first device in response to said load voltage changes.

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